Problems with perennial weeds in general and intra-row weeds in row crops in particular constitute the major weed problems in today’s organic cropping. Among the perennials, especially common couch (Elymus repens (L.) Gould), creeping thistle (Cirsium arvense L. Scop) and curled dock (Rumex crispus L.) and coltsfoot (Tussilago farfara L.) are causing problems in many crop rotations. Intra-row weeds are problematic due to the constant need for hand-weeding in several organic row crops.
Creeping thistle and coltsfoot
WEEDS seeks to obtain a better understanding of the biology of creeping thistle and coltsfoot specifically focussing on the allocation of carbohydrates to the belowground meristems: roots in the case of thistle and rhizomes for coltsfoot. We are working on a two-stringed work plan, the one looking at more fundamental aspects of carbohydrate allocation under the influence of growth disturbances such as tillage and mowing. The other string is seeking to integrate the fundamental knowledge with more strategic research aiming at developing rational weed control strategies that weakens the regenerative capacity of the two species.
Preliminary results from the fundamental studies have shown that the vulnerability of creeping thistle is most pronounced at the 8-10 true leave growth stage. How this knowledge is going to be utilized strategically is still to be clarified. Valid data for coltsfoot are still in preparation.
Effective control of couch-grass
Couch-grass and docks are to be controlled through new technology that makes a short-termed control campaign possible in order to retain nutrients in the root zone, which otherwise might be lost through leaching under a prolonged tillage strategy in the autumn. New technology developed in WEEDS is designed to uproot rhizomes of couch and taproots of docks. Rhizomes and taproots can then be removed from the field or destructed as an operation integrated with uprooting.
The first results have shown that repeated treatments with p.t.o. driven tools can uproot couch-grass rhizomes almost completely. The rhizomes can then be destructed by high pressure (>16kN). Taproots of docks did not show the same sensitivity to pressure. Composting the exposed rhizomes and taproots is another destruction method considered in the project.
Robotic intra-row weeding and punch planting
WEEDS is working on the development of an operational implement for automatic intra-row weed control. Several previous studies with different aspects of robotic weeding have revealed that the technology has become more mature in recent years and that an integration of the different technologies into an operational implement appears possible. WEEDS aims at making such an integration and subsequently investigate its performance under different weed control scenarios in various transplanted and punch planted row crops. However, the work is still in its infancy owing to some significant delays. Punch planting is a rather new technology with the ability to reduce and delay weed emergence.
The crop seeds are pressed into the soil with limited soil disturbance. WEEDS combines punch planting with stale seedbed strategies with the purpose of improving crop compatibility and the selectivity of subsequent post-emergence physical intra-row weeding. However, these advantages of punch planting have not yet been unambiguously confirmed, although weed emergence in slowly emerging crops, like onions, was markedly lower after punch planting.
Stale seedbed strategies as such gave significant reductions in weed emergence in most cases showing the usefulness of this technique as a relevant element in the control of intra-row weeds in row crops.
Weed control strategies in a wider context
Weed problems in organic cropping need to be managed in a broader context that also includes other cropping aspects such as crop rotation and nutrition. Consequently, the knowledge produced in WEEDS is integrated in an ongoing work on modelling weed proliferation in organic and conventional crop rotations under the influence of various cropping factors. The solidity of the weed control methods and strategies developed in WEEDS are judged and modified through analyses made with this weed modelling tool.
Bo Melander,
Faculty of Agricultural Sciences,
University of Aarhus,
Research Centre Flakkebjerg,
DK-4200 Slagelse
Phone: 89 99 35 00
E-mail: bo.melander@agrsci.dk
